At the present day a vast amount of information is dealt with in every phase of a civilized community. Among means which make the information communication smoother the print and the copy play an important part. Particularly, printing of relatively small numbers of copies falling in a category intermediate between the press-printing and hand-copying, that is, copies in the category of duplication printing tend to increase in quantity. To comply with such demand a copy duplicating machine for exclusive use in this category is eagerly desired. Among various printing systems of diverse principles an electrostatic printing system is believed to be most favorable because the printing operation requires no compression, is easy and dry, and is feasible at a higher speed. A wide variety of electrostatic printing systems have been proposed but a system without a substantial problem is not available. This invention utilizes the irradiation of light for the manufacture of a printing plate.
Photoresist methods are well known in the art; however, there exist many disadvantages. Long periods of exposure are necessary and complicated treatment to develop a photoresist image after the exposure are required for the manufacture of the printing plate. In order to prepare a printing plate more promptly recent researchers have been directed to the utilization of photoconductors which are presently used in the field of electrostatic photography. The photoconductor is of course considered to be highly excellent with respect to inter alia photosensitivity. However, the electroconductivity offered by the photoconductor is transient, ie., is effective only during its exposure to light and disappears immediately after the removal of light. Consequently, an electrostatic charge pattern obtained by charging the photoconductor and exposing it to a light image may not last for long periods. Such a short life of the charge pattern is not suitable for the printing of several or numbers of copies.